This invention relates to an arrangement for maintaining a plurality of molds at a predetermined temperature during molding of synthetic materials in said molds which are being pressurized by a common pressure source from which different fluids can be conducted to the molds.
In such known arrangements an operational problem generally exists, namely to maintain certain molds at preselected temperatures independently from each other. This operational problem appears in particular in injection molding, extrusion and blow forming processes. In such processes the molds must generally be maintained at a predetermined temperature which, in the injection molding and blow forming processes, cause solidification as a result of cooling of the plastified materials which have been fed into the molds. In this way the the molded plastic material can be removed from the molds as quickly as possible. The temperature which must be maintained in such processes needs to be sufficiently high so that the viscosity of the plastic material is such that it does not "set" prior to completely filling the mold. During extrusion the extrusion mold must generally be heated to such a degree to permit a continuous introduction of the extrusion strand with a flawless paying out and cooling of the extruded plastic material in a cooling bath.
It is of course general knowledge in the state of the art that molding machines are quite expensive and it is therefore important that such machines operate as efficiently as possible. In order to achieve this object it is necessary that the molds can be exchanged as rapidly as possible so that relatively short down times occur during exchange of different mold parts in a blow forming or injection molding process or exchange of a different extrusion profiled part in an extrusion process.
In order to achieve this object the connections to the molds are generally constructed as rapid couplings which can be easily detached and are constructed in such a way that when detached from the molds no fluid leaks out of the couplings or the molds proper.
Since the molds of the state of the art molding machines are generally water-cooled, water may remain inside the molds for considerable periods of time which can lead to corrosion of the interior of the molds. Moreover such rapid couplings are expensive and frequently malfunction. When rapid couplings are used in such machines which do not automatically seal when detached, fluids will leak out from the molds during detachment of the couplings which can lead to contamination and corrosion of the exterior of the molds and, much more seriously disadvantageous, to corrosion of the hollow interior surfaces of the mold.
It is also considered important in order to achieve an intense utilization of the molding machine to heat the molds to the desired temperature as quickly as possible.